The present invention relates to a method of and an apparatus for coating an automotive body, and more particularly to a method of and an apparatus for coating an automotive body automatically and efficiently by opening the doors and engine hood of the automotive body delivered along a conveyor line, thereafter coating inner panels of the automotive body, and closing the doors and engine hood.
Automotive bodies generally include coated outer panels which provide outer automobile appearances and also coated inner panels which are normally concealed from external view, such as inner peripheral walls of doors, body portions corresponding to the inner peripheral walls of the doors, reverse sides of an engine hood and a trunk lid, and inner walls of an engine compartment and a trunk.
In order to coat the inner peripheral walls of the doors and the corresponding body portions, it is necessary to open and close the doors. If other coated surfaces of the automotive body are not yet dried enough, the coating layers on these coated surfaces tend to be damaged when the doors are opened and closed.
Various arrangements have heretofore been proposed to open and close doors while avoiding damage to coated surfaces of automotive bodies. According to one conventional scheme disclosed in Japanese Laid-Open Patent Publication No. 58-95558, an engaging member is mounted on an angularly and vertically movable arm and brought into an window glass receiving slot in an automobile door or engaged by an auxiliary jig inserted in the window glass receiving slot. The door can then be opened and closed by displacing the arm.
When the arm is displaced to cause the engaging member to engage in the window glass receiving slot, it is highly difficult to guide the engaging member accurately into the window glass receiving slot since the opening of the window glass receiving slot is considerably narrow. Moreover, automotive bodies may not always be delivered into a correct position, and doors may be opened to irregular angular extents depending on different automotive bodies.
If the auxiliary jig is to be mounted in the window glass receiving slot, then it is necessary to attach the auxiliary jig to the door in advance. Therefore, the efficiency of operation is poor, and it is impossible to provide a highly efficient, automated coating process.
Apparatus for opening and closing various covers such as engine hoods, trunk lids, or the like are disclosed in Japanese Laid-Open Utility Model Publications Nos. 55-2441, 59-15469, 59-106586, for example. The cover opening and closing apparatus disclosed in Japanese Laid-Open Utility Model Publication No. 55-2441 has an actuatable arm extending from a structural member disposed above an automotive conveyor apparatus. According to Japanese Laid-Open Utility Model Publication No. 59-15469, an arm is mounted on a coating station movable alongside of and parallel to an automotive body conveyor apparatus, and movable in overhanging relation to an automotive body to open and close a cover thereof. In each of the disclosed arrangements, the arm is lowered from above the automotive body, caused to grip a portion of the cover, and then displaced upwardly to open the cover.
However, these disclosed systems have had various problems as described below. While the automobile assembling plant is in operation, dust suspended in the space in the plant is deposited on the arm. When the arm is lowered toward an automotive body, the deposited dust on the arm falls onto the automotive body, contaminating a surface to be coated of the automotive body. The surface to be coated of the automotive body is cleaned before a coating layer is applied thereto, and any dust or foreign matter attached to the surface will cause a serious coating problem when the coating layer is applied. Oil or grease supplied to articulations of the arm also tends to drop onto the automotive body, resulting in a coating failure.
A cover holding apparatus for holding the opened cover in a prescribed angular position is disclosed in Japanese Laid-Open Utility Model Publication No. 60-148187, for example. The disclosed cover holding apparatus comprises a first rod member having one end supported on a carriage for placing an automotive body thereon, and a second rod member angularly movably engaging the other end of the first rod member and engageable with the reverse side of the cover. The first and second rod members can be locked to each other at respective angular positions by means of a locking means including a spring.
The cover holding apparatus of this type is however large and heavy, cannot easily be handled, and may damage outer panels of automotive bodies when it is attached to and detached from covers.
Articulated coating robots have widely been used for coating inner panels of automotive bodies. An articulated coating robot is normally installed on the floor in a coating booth. Therefore, a space for installing the coating robot must be provided on the floor in the coating booth. As a consequence, the coating booth is large in size, and the floor thereof disturbs a stream of air which flows downwardly in the coating booth to prevent paint mists from being scattered. With a view to solving this problem, there has been proposed a coating apparatus in which only an arm with a paint spray gun mounted on its distal end is inserted in a coating booth (see Japanese Laid-Open Patent Publication No. 61-222566). With only the arm inserted in the coating booth, however, the range of movement of the nozzle of the paint spray gun is limited to a considerably small range.
When doors of an automotive body and corresponding inner panel portions of the automotive body are coated by a coating robot, a plurality of paint spray nozzles are directed toward front and rear doors and coat them simultaneously, and a plurality of other paint spray nozzles are also directed to automotive body portions and coat them simultaneously. The paint spray nozzles eject paint sprays while they are very close to each other, ejected paint sprays tend to be applied to the nozzles and the arms.